using MP.Core.DTO;
using StackExchange.Redis;

namespace MP.RIOC.Services
{
    public class RedisWeightProvider : IWeightProvider
    {
        #region Public Constructors

        public RedisWeightProvider(IConnectionMultiplexer mux, IConfiguration config)
        {
            _config = config;
            _db = mux.GetDatabase();
            _mux = mux;
            _defaultOld = config.GetValue<int>("RouteMan:DefaultWeightOld", 100);
            _defaultNew = config.GetValue<int>("RouteMan:DefaultWeightNew", 0);
            _redisBaseKey = config.GetValue<string>("ServerConf:RedisBaseKey") ?? "MP_IOC";
            _keyPrefix = $"{_redisBaseKey}:route_weight:";
        }

        #endregion Public Constructors

        #region Public Methods

        /// <summary>
        /// Ritorna (oldWeight, newWeight) per il metodo. Se non esiste, crea la chiave con i default.
        /// </summary>
        public (int oldWeight, int newWeight) GetWeightsFor(string method)
        {
            if (string.IsNullOrEmpty(method)) method = "unknown";
            var key = _keyPrefix + method;

            // Leggi entrambi i campi
            var oldVal = _db.HashGet(key, "old");
            var newVal = _db.HashGet(key, "new");

            // Se entrambi mancanti, inizializza con default (usando HSet con When.NotExists per evitare overwrite)
            if (oldVal.IsNull && newVal.IsNull)
            {
                // Imposta i campi singolarmente con When.NotExists per evitare overwrite
                _db.HashSet(key, "old", _defaultOld, When.NotExists);
                _db.HashSet(key, "new", _defaultNew, When.NotExists);

                // Rileggi per essere sicuri
                oldVal = _db.HashGet(key, "old");
                newVal = _db.HashGet(key, "new");
            }

            // Se uno dei due manca, impostalo al default (non sovrascrive l'altro)
            if (oldVal.IsNull)
            {
                _db.HashSet(key, "old", _defaultOld, When.NotExists);
                oldVal = _defaultOld;
            }
            if (newVal.IsNull)
            {
                _db.HashSet(key, "new", _defaultNew, When.NotExists);
                newVal = _defaultNew;
            }

            if (!int.TryParse(oldVal.ToString(), out var oldW)) oldW = _defaultOld;
            if (!int.TryParse(newVal.ToString(), out var newW)) newW = _defaultNew;

            // clamp 0..100
            oldW = Math.Clamp(oldW, 0, 100);
            newW = Math.Clamp(newW, 0, 100);

            return (oldW, newW);
        }

        // API per aggiornare i pesi a runtime (opzionale)
        public void SetWeights(string method, int oldWeight, int newWeight)
        {
            var key = _keyPrefix + (string.IsNullOrEmpty(method) ? "unknown" : method);
            _db.HashSet(key, new HashEntry[] {
            new HashEntry("old", Math.Clamp(oldWeight,0,100)),
            new HashEntry("new", Math.Clamp(newWeight,0,100))
        });
        }

        public async Task<List<WeightDTO>> GetAllWeightsAsync()
        {
            var result = new List<WeightDTO>();
            var server = _mux.GetServer(_mux.GetEndPoints().First());

            if (server.IsReplica)
            {
                return result;
            }

            await foreach (var key in server.KeysAsync(pattern: $"{_keyPrefix}*"))
            {
                var methodName = KeyToString(key.ToString());
                if (string.IsNullOrEmpty(methodName)) continue;

                var oldVal = _db.HashGet(key, "old");
                var newVal = _db.HashGet(key, "new");

                int oldW = 100;
                int newW = 0;

                if (!oldVal.IsNull && int.TryParse(oldVal.ToString(), out var parsedOld))
                    oldW = Math.Clamp(parsedOld, 0, 100);

                if (!newVal.IsNull && int.TryParse(newVal.ToString(), out var parsedNew))
                    newW = Math.Clamp(parsedNew, 0, 100);

                result.Add(new WeightDTO { Method = methodName, OldWeight = oldW, NewWeight = newW });
            }

            // riordino desc x NEW poi alfabetico...
            result = result
                        .OrderByDescending(x => x.NewWeight)
                        .ThenBy(x => x.Method)
                        .ToList();

            return result;
        }

        public bool UpsertWeight(WeightDTO updRecord)
        {
            if (updRecord == null || string.IsNullOrEmpty(updRecord.Method))
                return false;

            var key = _keyPrefix + updRecord.Method;
            _db.HashSet(key, new HashEntry[] {
            new HashEntry("old", Math.Clamp(updRecord.OldWeight, 0, 100)),
            new HashEntry("new", Math.Clamp(updRecord.NewWeight, 0, 100))
        });

            return true;
        }

        private string KeyToString(string key)
        {
            if (string.IsNullOrEmpty(key)) return "";
            var prefix = _keyPrefix ?? "";
            if (key.StartsWith(prefix))
                return key.Substring(prefix.Length);
            return key;
        }

        #endregion Public Methods

        #region Private Fields

        private static string _keyPrefix = "route_weight:";
        private static string _redisBaseKey = "";
        private readonly IConfiguration _config;
        private readonly IDatabase _db;
        private readonly IConnectionMultiplexer _mux;
        private readonly int _defaultNew;
        private readonly int _defaultOld;

        #endregion Private Fields
    }
}